As a representative of thin-film transistor (TFT), oxide semiconductor thin film transistor is considered as the next generation of thin film transistor (TFT) used in displays.
In a TFT drive substrate, a typical transparent metal oxide material used for fabricating an oxide semiconductor layer is indium gallium zinc oxide (IGZO). Since the thin-film transistor made of IGZO (referred to as “IGZO thin-film transistor” below) has good flexible property and electrical property, and the processing temperature during the manufacture is low, the IGZO thin-film transistor is suitable to be used for forming flexible substrate. But the substrate made of IGZO has poor stability in air, and it is sensitive to oxygen and moisture, since oxygen and moisture may pass through the protection layer on the IGZO and deteriorates the property of the amorphous IGZO. Therefore, there is a need for provide a high-quality protective film on the IGZO to improve the stability of the TFT substrate.
Traditional IGZO thin film transistor substrate has a etch blocking structure on a IGZO layer, that is, a etch blocking layer made of SiNx or SiOx, thus the IGZO layer is protected and not destroyed when the source/drain electrode is fabricated, thereby enhancing the stability of the TFT substrate.
For example, as shown the FIG. 1, a structure of an IGZO thin film transistor in prior art is illustrated. The IGZO thin film transistor comprises: a gate metal layer 11 formed on a substrate; a gate insulating layer 12 formed on the gate metal layer 11; an oxide semiconductor layer 13 formed on the gate insulating layer 12; a blocking layer 14 (for example, the blocking layer is made of SiOx) formed on the IGZO semiconductor layer 13; a source/drain metal layer 15 formed on the blocking layer 14, the IGZO semiconductor layer 13 and the gate insulating layer 12; a passivation layer 16 formed on the source/drain metal layer 15, the gate insulating layer 12 and a part of the blocking layer 14; and a pixel electrode 17 formed on the passivation layer 16. Herein, the pixel electrode 17 is not a part of the IGZO thin film transistor, and it is necessarily to fabricate only when the display device, such as an array substrate, is to be produced.
The problem of the above-mentioned IGZO thin film transistor is that: the stability of the IGZO thin film transistor is still bad, since the interface characteristic and the crystal lattice match between the IGZO semiconductor layer and the gate insulating layer as well as the blocking layer is bad.